Reddit mentions of Joe Celko's SQL for Smarties: Advanced SQL Programming (The Morgan Kaufmann Series in Data Management Systems)

First don't think of this as "DBA" stuff - you're a developer, you need to know database technology, period. Read this rant by Dennis Forbes in response to Digg's CTO's complaints about databases it's very reminiscent of TFA.

Read Data and Reality by the late William Kent (here's a free copy) and get a fundamental understanding of "information" vs. "data". Then read Information Modeling and Relational Databases to pickup a couple practical approaches to modeling (ER & OR). Now read The Datawarehouse Toolkit to learn dimensional modeling and when to use it. Practice designing effective models, build some production databases from scratch, inherit some, revisit your old designs, learn from your mistakes, write lots and lots and lots of SQL (if you want to get tricky with SQL I suggest to pickup Celko's SQL for smarties - it's like the Hacker's Delight for SQL).

Many strange models you may encounter in the wild are actually optimizations. Some are premature, some outright stupid, and some brilliant, if you want to be able to tell one from the other then you're going to dive deep into internals. Do this generically with Modern Information Retrieval and Managing Gigabytes then for specific RDBMSs Pro SQL Server Internals, PostgreSQL Internals, Oracle CORE, etc.

Reflect on how awesome practically every modern RDBMS is as a great technological achievement for mankind and how wonderful it is to be standing on the shoulders of giants. Roll your eyes a little bit whenever you overhear another twenty-something millenial fresh CS graduate who skipped every RDBMS elective bleat about NoSQL, Mongo, whatever. Try not to fly into murderous rage when another loud-mouthed know-nothing writes at length about how bad RDBMS technology is when they couldn't be bothered to learn the most basic requisite skills and knowledge to use one competently.

You may want to read SQL for Smarties.

It does a very good job of stressing the importance of adjusting your thinking when you're working with a relational DB. If you approach SQL as if it were a procedural language, you will hate it, your results will suck, and DBAs (and devs who are competent at SQL) will make fun of you.

for years I've recommended going through SQL for Smarties which in the years since I had it seems to have grown to be three times its size, but nevertheless describes relational databases and SQL querying from the classical DBA perspective. He also has SQL Puzzle books that are also great. If you go through Celko's books you'll really have a sense for how a relational database was really meant to be used, and when you see someone touting MongoDB queries you'll just laugh your ass off.

Yeah, forget PHP, and probably forget any book that attempts to teach both PHP and SQL. Unfortunately, good books on SQL are actually rather few and far between. I can recommend Understanding The New SQL, but it's quite old - buy it used. For more advanced stuff, SQL For Smarties is also quite good.

Not SQLServer specific, but Joe Celko's "SQL For Smarties" is a great reference for all things SQL: http://www.amazon.com/Joe-Celkos-Smarties-Fourth-Edition/dp/0123820227

For anyone who wants to go beyond 'this is a select... this is an insert... this is a join..' check out this book:

http://www.amazon.com/Joe-Celkos-Smarties-Fourth-Edition/dp/0123820227

He always follows the SQL standard, but... some things don't implement it, so everything in this books is not guaranteed to work with all (or even any) RDBMS.

Agreed, OP, you're massively overcomplicating this. If you learn a bunch of math and theory to try and become a database professional you will just come across as an academic rather than someone who can get work done. Learn how to get work done. Check out books like SQL Cookbook and SQL For Smarties to learn stuff that will actually help you do what you need to do.

You do want to have normalization down and basically understand set theory, but you're already doing that.